Towing hooks, which are employed to tow vehicles, have been detachable so as to be attached to the vehicles only when the vehicles are towed. In such mounting structures of the towing hooks, a nut is welded to an end of a side-member of a vehicle body and a towing hook, which possesses a length so that a distal end of the towing hook projects from a bumper face, is attached to the nut. However, in a situation where a distance between the distal end of the towing hook and an attachment portion of the towing hook is long, when the towing hook is applied with load in a width direction of the vehicle, the towing hook may impact the bumper face so that the bumper face may be damaged.
In the light of the foregoing, a mounting structure of a towing hook has been suggested in order to solve the above-described matters, in which the towing hook is attached to a bumper reinforcement between a side-member of a vehicle body and a bumper face. For example, JP2001-63498A (reference 1) discloses a structure where a bracket having a threaded part is secured to a front surface of a bumper reinforcement so that a towing hook is attached to the bumper reinforcement via the bracket. Further, JP2005-186846A (reference 2) discloses a towing hook attachment structure, in which a towing hook mounting bracket is inserted into a front wall of a bumper reinforcement, and a flanged bolt is inserted from a back side of the bumper reinforcement and is threadedly engaged with the towing hook mounting bracket. The towing hook is then attached to a front wall of the towing hook mounting bracket. Still further, JP2006-36158A (reference 3) discloses a towing hook mounting structure, in which a towing hook attachment bracket and a strength member are housed inside a bumper reinforcement. The towing hook attachment bracket penetrates through front and back surfaces of the bumper reinforcement.
When the vehicle is towed via the towing hook, the towing hook bears load in longitudinal and width directions of the vehicle. Meanwhile, when the vehicle is shipped, the towing hook bears load in a downward direction of the vehicle. According to any of the above described towing hook mounting structures, the towing hook is attached to a relatively weak-structured bumper reinforcement so that the towing hook may not be firmly attached to the bumper reinforcement. In such circumstances, when the towing hook is applied with the load, the attachment portion of the towing hook may suffer deformation and damage.
Further, according to the structures disclosed in the references 2 and 3, some components are housed within a sectional area of the bumper reinforcement that serves as an energy-absorbing function. The bumper reinforcement can serve as the energy-absorbing function when being distorted in a cross-section. In such circumstances, those components disturb the cross-sectional distortion so that the bumper reinforcement cannot perform properly as the predetermined energy-absorbing function.
Still further, where a towing hook-mounting unit is secured to a bumper reinforcement by welding or the like, a predetermined welding strength may be impaired due to thermal affect.
The present invention has been made in view of the above circumstances, and provides a mounting structure of a towing hook, which mounting structure can ensure an energy-absorbing function that is achieved when a bumper reinforcement is deformed in a cross section in a collision and can protect an attachment portion of the towing hook from being bent and damaged even when the towing hook is applied with load.